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\begin{equation*}\frac{DF(P_0)}{DP}\ =F[P_0,P_1]=\frac{F(P_1)-F(P_0)}{P_1-P_0}=F'(P_0\!<\!P\!<\!P_1)=\sum_{TN=1}^{UT=\infty}\frac{F'(P_{(tn)})}{UT},\,\!\end{equation*}
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